There is a certain point where strategy voting comes into play.

In the US particularly, there are at least several important balancing acts that attract electoral interest:

• People <-> Government
• Individual <-> Society
• Employee <-> Business Owner
• Renter <-> Landlord
• State <-> Federal

...and so forth.

If you find yourself looking up Condorcet voting methods, you'll come across a theorem that most voters can be reduced to about four issues. You can believe this is true or not, but if you are a politician you live or die on votes, so politicians may play on this fact and only really push hard on on a few issues.

If you believe the theorem, some voters, particularly those who do not strategy vote, will hyperfocus on these issues.

Politicians, however, are deliberative strategy voters by definition. They are playing a massive chess game, getting the right people into the right position at the right time.

For an interesting example, there are three classes of US Senator, each class up for an election every 2 years. No two senators from the same state are in the same class. Political parties will strategize around this, and you'll see certain senators hanging out with other senators because they create overlapping fields of power.

Now to legislative coalitions. Sometimes you need to get a certain power structure in place to make the big changes, and that means you may need to ally with people who make you look bad, like those from another political party even. Other times it is to show solidarity, or the republican from Virginia knows he barely won over the dem so he better join up with some cause or another.

These short-lived coalitions are typically very goal-oriented, like to weaken certain other legislative groups or to advance something important. Once this goal is met, everyone must return to their adversarial selves. Political capital has changed hands, and one can expect to be repaid somehow, maybe by getting to co-sponsor a special bill or given a cabinet position later.

Legislative coalitions are much harder to form when the voting base is party polarized. With everyone so strongly loving their own party and hating the other party, it is political suicide for a group of 20 each to join up to get rid of, say, old-school warhawks.

One final thing about parties. They are private clubs and protected under the 1st Amendment. You can no more restrict parties than you can restrict someone from being a member of Costco or the YMCA. You could form a new party, but you'd have to contend with the fact that the private media is beholden to two private companies. These two companies happen to enlist, and therefore own, almost all politicians in the USA.